No difference in PROMs between kinematic and mechanical alignment in TKA: An umbrella review with secondary meta-analysis and GRADE assessment.

Abstract

Purpose: To identify, synthesise and critically appraise the findings of meta-analyses that compare patient-reported outcome measures (PROMs) between unrestricted kinematic alignment and mechanical alignment in total knee arthroplasty (TKA). It was hypothesised that some meta-analyses inaccurately combine PROMs from unrestricted and restricted kinematic alignment techniques.

Methods: Two authors independently screened articles based on inclusion and exclusion criteria and assessed the methodological quality based on the 16 domains of A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2). Effect sizes of difference in PROMs were tabulated for each meta-analysis. Studies included in the meta-analyses were assessed to determine if they were on true unrestricted kinematic alignment. A secondary meta-analysis excluded studies on restricted kinematic alignment techniques, to recalculate pooled estimates (mean difference (MD) with their 95% confidence interval (CI)) of the Knee Society Score (KSS), Oxford Knee Score (OKS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Forgotten Joint Score (FJS). The quality of evidence was assessed using the GRADE.

Results: There were 15 meta-analyses pooling data from 39 clinical studies eligible for data extraction. None fulfilled all seven critical AMSTAR-2 domains. Some reported kinematic alignment yielded superior KSS (Function, n = 9; Knee, n = 6: Combined, n = 8), OKS (n = 7), WOMAC (n = 8) and FJS (n = 1). The secondary meta-analysis included only studies on unrestricted kinematic alignment and results at the latest follow-up, for which the mean and standard deviations were reported and revealed no difference in KSS, OKS, WOMAC or FJS between kinematic and mechanical alignment. GRADE analysis revealed 'very low' quality of evidence for KSS, WOMAC and FJS, while it was 'low' quality for OKS.

Conclusion: Current evidence suggests no difference in PROMs between kinematic and mechanical alignment in TKA. Meta-analyses that report the contrary often need more rigour as they pool studies on various kinematic alignment techniques or represent the same cohort at different times. Orthopaedic societies should promote using objective outcome measures to evaluate and compare alignment techniques.

Registration: Systematic review protocol registration (Prospero: CRD42023434713).

Level of evidence: Level III.